This invention relates to a novel diene copolymer composition for use in hot melt adhesives. More particularly, it relates to diene block copolymer adhesive compositions containing acrylic monomers.
It is known that a block copolymer can be obtained by an anionic copolymerization of conjugated dienes or such dienes and an alkenyl arene compound by using an organic alkali metal initiator. For example, block copolymers have been produced which comprise primarily those having a general structure EQU A--B and A--B--A
wherein the polymer blocks A comprise thermoplastic polymer blocks of alkenyl arenes such as polystyrene, while block B is a polymer block of a conjugated diene such as polybutadiene or polyisoprene. They may be linear, radial, star, tapered and/or asymmetric and hydrogenated or unhydrogenated. The proportion of the thermoplastic blocks to the elastomeric polymer block and the relative molecular weights of each of these blocks is balanced to obtain a rubber having unique performance characteristics.
It is well known that these polymers are useful in formulating hot melt adhesives. Such polymers are especially useful in formulating hot melt adhesives that are superior in adhesion to nonpolar surfaces. Nonrubber acrylic adhesives are known to be useful for making adhesives that are superior in adhesion to polar surfaces, presumably because of favorable energetics between the polar acrylic functionality and the surface polarity. It would be advantageous to provide a hot melt adhesive composition which was based on a rubbery or elastomeric polymer but which also has superior adhesion to polar surfaces. The present invention provides such a hot melt adhesive composition.